Water flow detectors having a timer responsive to movement of a lever connected to a paddle are known. A known water flow detector uses an air bleed timer. U.S. Pat. No. 6,331,820, entitled Explosion Proof Water Flow Detector, issued Dec. 18, 2001, discloses a paddle type flow detector which relies on an air bleed timer. U.S. Pat. No. 4,782,333, entitled Water-flow Detector With Rapid Switching, issued Nov. 1, 1988, discloses an air bleed timer. Both of these patents are assigned to the assignee hereof and incorporated herein by reference.
In general a water flow detector using an air bleed timer has a cam. The cam, when in a first position, maintains a switch assembly in a first state. The cam when in a second position enables the switch assembly to move to a second state. The lever when moved to a second position enables the cam to move from the first position to the second position.
The time it takes the cam to move depends upon the rate at which air is set to bleed out of an air chamber formed by a diaphragm. If the air is set to bleed out quickly, the cam will move quickly from the first to the second position. If the air is set to bleed out slowly, the cam will move slowly from the first to the second position and it will take longer for the switch to move from the first to the second state.
The lever is moved from the first position to the second position by the flow of water in a riser pipe of a fire sprinkler assembly. The water causes the paddle to move from a first to a second position. If the lever is not in the second position, the cam cannot move from the first to the second position. Accordingly the switch can not move from the first state to the second state. Whether the cam moves from the first to the second position depends on the rate of air bleed and the duration of suitable water flow.
If the water flow stops before the air bleed is complete, the cam will be moved back to the first position by the lever prior to the cam moving to the second position. The switch will not move to the second state. For instance, if the bleed duration is 50 seconds then the cam will move from the first to the second position in 50 seconds so long as the lever is maintained in the 2nd position by the water flow.
If the lever is not maintained in a second position by the water flow for 50 seconds then the cam will not be able to move to the second position. The switch will not move to the second state. Accordingly the longer the bleed time, the longer the water flow most continue for the switch to move from the first to the second state. The shorter the bleed time the shorter amount of time the water flow most continue for the switch to orient from the first state to the second state.
Another embodiment is disclosed in pending U. S. application Ser. No. 12/974,637 filed Dec. 21, 2010 and entitled, Water Flow Detector. The '637 application is assigned to the assignee hereof and incorporated by reference.
While timers of the type described above have been found to be useful in providing needed delays, it would be desirable to be able to reduce their complexity and cost while still providing an adjustable time delay.